Answer:
c. expanded polyurethane
Explanation:
Thermal performance of a building fabric is measured in terms of heat loss and is expressed as U-value or R-value. U-value is the rate of heat transferred through a structure divided by the difference in temperature across the structure with a unit of measurement of W/m²K.You can calculate the U-value of a by getting the reciprocal of the sum of thermal resistances , R, making the building material.
If you have the value of R, then U=1/R
Material size R U
plywood 1" 1.25 0.8
Poured concrete 2" 0.99 1.010
Expanded polyurethane 1" 6.5 0.1538
Asbestos shingles 1" 0.03 33.33
The material with lowest U-value is expanded polyurethane
Answer:
3.735×10⁻⁶ N
Explanation:
From newton' s law of universal gravitation,
F = Gmm'/r² .............................. Equation 1
Where F = Gravitational force between the person and the refrigerator, m = mass of the person, m' = mass of the refrigerator, r = distance between the person and the refrigerator. G = gravitational universal constant.
Given: m = 70 kg, m' = 200 kg, r = 0.5 m
Constant: G = 6.67×10⁻¹¹ Nm²/kg².
F = (6.67×10⁻¹¹×70×200)/0.5²
F = 93380×10⁻¹¹/0.25
F = 373520×10⁻¹¹
F = 3.735×10⁻⁶ N
Hence the force between the person and the refrigerator = 3.735×10⁻⁶ N
Solar photovoltaic cells, or solar panels, are arrays of silicon cells that can transforms light radiation into electricity. Solar heating system absorbs the heat from the sun and either transform it into electricity through s generator or uses the energy to heat homes and water.
I believe it is an electromagnet
